FIG. 1 depicts a prior art—a feed control device described in Japanese Patent Application Publication No. 2009-240053. The device is connected, through a cable, with a power supply side plug (PP) which can be connected to an external power supply such as, for example, a commercial AC (alternate current) power supply. The device is also connected, through a cable, with a vehicle side plug (CP) which can be connected to a vehicle (e.g., an electrically-powered car). The device is configured to control power feeding from the external power supply to the electrically-powered car. This feed control device is used to turn on and off the power to a charge circuit configured to charge a battery, which a vehicle such as a battery car or a plug-in hybrid car is equipped with.
In this sort of feed control device, when the battery of an electrically-powered car is charged, there is a problem causing electrical leakage from the high-tension side of the device to the car body. Accordingly, a feed line inside the device is provided with a relay for electrically connecting a power supply side plug and a vehicle side plug. The relay is configured, if the electrical leakage is detected, to open contacts of the replay to shut off the power to the electrically-powered car.
Returning to FIG. 1, the device includes, between the power supply and the electrically-powered car, a first electrically-conducting path (L1) corresponding to a live (hot) wire, a second electrically-conducting path (L2) corresponding to a neutral wire and a third electrically-conducting path (L3) corresponding to a ground wire. The device also includes a relay (10), a controller circuit (12), a power supply circuit (11) and a zero phase current transformer (ZCT). The relay (10) is inserted into the paths (L1 and L2) and is used to turn on and off the power to the electrically-powered car from the power supply. The control circuit (12) is connected to the electrically-powered car through fourth electrically-conducting path (L4) as a signal wire, and is configured to turn the relay (10) on and off in accordance with a control signal obtained from the electrically-powered car through the signal wire (L4). The power supply circuit (11) is connected to the paths (L1 and L2) between the power supply side plug (PP) and the relay (10) as well as the path (L3), and is configured to produce electric power supplied to the controller circuit (12) and so on. The paths (L1 and L2) between the power supply side plug (PP) and the relay (10) are inserted into a zero phase current transformer (ZCT). The transformer (ZCT) is configured, if unbalance occurs in electric currents flowing through the paths (L1 and L2), to generated an induced current according to an unbalance current between the paths (L1 and L2).
If the controller circuit (12) detects electrical leakage based on an induced current obtained from the zero phase current transformer (ZCT), the circuit (12) turns off the relay (10) to shut off the power to the electrically-powered car side. Therefore, the controller circuit (12) and the relay (10) function as an earth leakage breaker.
When the vehicle side plug (CP) is connected to the electrically-powered car with the power supply side plug (PP) connected to the external power supply, it is undesirable that voltage is output to the plug (CP). Accordingly, the controller circuit (12) keeps the relay (10) off until a charging start command is entered into the circuit (12) from the charge circuit side of the electrically-powered car after the plugs (PP) and (CP) are connected to the external power supply and the electrically-powered car, respectively.
In the feed control device, voltage may be output from the vehicle side plug (CP) just as the power supply side plug (PP) is connected to an external power supply in case contacts of the relay (10) are welded (stuck) together by arc generated when the relay (10) is turned on and off.